High-frequency electron discharge apparatus



Jan. 4; 1944. FREMLlN 2,338,237

HIGH FREQUENCY ELECTRON DISCHARGE APPARATUS Filed Dec. 10, 1940 TOSIGNAL MODl/M 7' IIVG Sou/r65 T0 JIGML MODl/LA TING SOURCE IN VEN TORJOHN HEAVEI? FfiEMU/V ATTORNEY Patented Jan. 4, 1944 UNITED STATES vPATENT- Fl=lCE azaazs'z HIGH-FREQUENCY ELECTRON DISCHARGE John BeaverFremlin, London, England, asaignor to International Standard ElectricCorporation,

New York, N. Y.

Application December 10, 1940, Serial No. 369,431

In Great Britain December 22, 1939 Claims. (CL 250-275) This inventionrelates to ultra-high frequency apparatus comprising resonators of thecavity type.

It is proposed, in accordance with the invention, to modulate or changethe frequency of a resonator of the cavity type by varying thedielectric constant withina portion of the reso-v nator, by varying anelectronic space charge or by varying the intensity or velocity of anelectron beam traversing that portion.

The invention is primarily applicable to electron discharge apparatususing the principles of velocity modulation of electrons for theexcitation of a resonator effective at very high frequencies.

Briefly such apparatus usually comprises a single resonator or a pair ofcoupled resonators of cavity type, electrons being passed through twosuccessive gaps therein to be modulated in velocity in the first gap andto yield energy at the second gap for the maintenance or oscillations.

In either single or double resonator apparatus utilising velocitymodulation of electrons, an auxiliary electron beam may be fired acrosssome part of one of the resonators. This auxiliary beam, if of suitablevelocity will change the dielectric constant and hence the naturalfrequency of the resonator. In the case of a single resonator,therefore, modulation of the auxiliary beam will give a frequencymodulation of the high frequency output, while in a double resonator itwill give an amplitude modulation (owing to the detuning of oneresonator with respect to the other), probably combined with some degreeof frequency modulation.

The illustration of the single cavity and double cavity tubes inaccordance with this invention are shown in the drawing in which, Fig. 1shows a single cavity arrangement, and Fig. 2 a double cavityarrangement.

In the drawing the illustrations are made diagrammatically.

In Fig. 1 an electron emitting cathode l0 emits electrons which areaccelerated by accelerator electrode I l and centered by the controlelectrode l2 to produce a cathode beam shown in dotted lines at l3. Thisbeam is transmitted through a pair of grids l4, l5, located in the wallof resonant cavity l6 and tube ll, respectively, after which it is againsubject to the effect of a control potential between grid l8 and the endwall of chamber it. Such a tube is known in the prior art and energy maybe extracted from the tube due to the retarding effect caused between l8and the end wall.

In accordance with my invention modulation of the signal beam isprovided by means of a second beam traversing the cavity through whichthe beam passes so as to change the dielectric constant effective inthis area. Thi is accomplished by a cathode 20, an acceleratingelectrode 2| to which a signal modulating source is coupled, aconcentrating electrode 22 to form the electrons emitted from cathode 20into a beam,

and a target electrode 23 which serves to prevent electrons from thebeam from returning into the space. The signal modulations applied toelectrode 2| serve to vary the concentration of the beam emitted fromcathod 20 and so to vary the tures shown invFig. 2 may, if desired, beapplied to Fig. 1 and similarly the features of Fig. 1 which differ fromFig. 2 may be applied to this other arrangement.

What is claimed is:

1. High frequency discharge apparatus including a tube, means coaxialwith and surrounding said tube, forming a hollow resonant chamber, aplurality of aligned grids, one in one end of said means, a second inone end of said tube and adjacent said first grid, and a. third at theother end of said tube, a source of electrons aligned with said gridsand adapted to discharge and-direct electrons along ,a path through allof said grids, and means for varying the dielectric constant of saidchamber, comprising a second source of electrons and a target positionedwithin said chamber, forming an electron discharge path across saidchamber between said third grid and the other end of said resonantchamber forming means.

2. Modulated high frequency discharge apparatus comprising a hollowresonator having a predetermined dielectric constant, means formaintaining oscillations in the resonator including means for directinga stream of electrons along a main discharge path through the resonator,and means for modulating said oscillations including means for directinga second stream of electrons along a second discharge path through theresonator and means for modulating said second stream.

3. Modulated high frequency discharge apparatus as set forth in claim 2,including means for velocity modulating the first stream of electrons inone part of the resonator, and means for transferring energy from saidstream to the oscillating field in a second part of the resonator, andin which the second stream of electrons passes through said second partof the resonator.

4. Frequency modulated high frequency discharge apparatus comprising ahollow resonator having a predetermined dielectric constant and anoscillation frequency determined by said constant, means for maintainingoscillations in the resonator including means for directing a stream ofelectrons along a main discharge path through the resonator, and meansfor modulating the frequency of said oscillations including mean fordirecting a second stream of electrons along a 20 second discharge paththrough the resonator and means for modulating said second stream.

5. Amplitude modulated high frequency discharge apparatus comprising ahollow resonator having a predetermined dielectric constant and formedwith two resonant cavities, means for maintaining oscillations in theresonator including means for directing a stream of electrons along amain discharge path passing through both cavities of the resonator, andmeans for amplitude modulating the frequency of said oscillationsincluding means for directing a second stream of electrons along asecond discharge path through the second cavity of the resonator,located adjacent the discharge end of the first stream of electrons, andmodulating said second stream, said detuning action of one cavity withrespect to the other producing amplitude modulation.

JOHN HEAVER FREMLIN.

